Age and growth study of two fin fish species from a tropical estuary

Abstract

Data on two fin fish species were collected from the Cochin estuary (part of the Vembanad–Kol wetland system) from January 2018 to December 2019. The present study presents the first findings on fisheries demographics in these estuaries, based on length–frequency​ data, to calculate vital demographic dynamic factors and estimate the stock of these commercially important fish species. A variety of evaluations was conducted using the FiSAT II program. Pseudetroplus maculatus had an asymptotic length (L) of 97.6 mm as well as a growth constant (K) of 1.2 year-1. For all the species studied, the age at zero-length (t0) had been calculated and varied from −0.095 to −0.2. Gerres setifer had longevity (tmax) of 5.66 years and a growth performance index (ϕ) of 4.03, whereas P. maculatus had 2.5 and 4.06. P. maculatus had overall mortality (Z), natural mortality (M), and fishing mortality (F) of 3.04, 1.45, and 1.58 year1, respectively, while G. setifer had 1.14, 0.77, and 0.37 year1. The present exploitation level is greater than the optimum exploitation rate, according to the relative yield per recruit (Y/R) study, indicating over-exploitation of three examined finfish species and moderate exploitation for two species. Management measures such as mesh size limitations, restricted fishing efforts, and the proclamation of restricted seasons are required to save these species from extinction.